1. Field of the Invention
The present invention relates in general to porous cellulose fibers having a plurality of micropores, which are used as a material of a catalyst support for supporting a nano-metal catalyst, thus maximizing the increase in catalytic reaction activity even when used in a small amount in various catalytic reactions, and to a method of preparing a nano-metal-supported catalyst using the same. More particularly, the present invention relates to a method of preparing a nano-metal-supported catalyst, including subjecting cellulose fibers cut to a predetermined length, to special treatment, thus preparing a catalyst support, growing carbon nanotubes on the surface of the catalyst support, and supporting a nano-metal catalyst on the surface of the grown carbon nanotubes, to a nano-metal-supported catalyst including a cellulose catalyst support, and to the use of cellulose fibers as a catalyst support for supporting a nano-metal catalyst.
2. Description of the Related Art
Recent research into catalysts is conducted toward the development of a catalyst support having a large surface area and the preparation of a catalyst metal on a nano scale. In particular, the development of a novel catalyst support material, which has a large surface area and is inexpensive to prepare, is regarded as more valuable.
Useful as a catalyst support in the present invention, cellulose fibers are a material that is easily purchased and is very inexpensive, and are widely used as a lightweight composite material, an adsorption and filtration material, or a reinforcing agent, due to the greatly superior intrinsic properties in terms of surface area, porosity, and physical strength. However, research into the use of cellulose fibers as a catalyst support through a series of procedures has not yet been performed domestically or abroad. Considering that conventional catalyst supports, such as mesoporous carbon, activated carbon, carbon black and so on, suffer from high preparation costs, the use of cellulose fibers creates incredible value and enables the development of novel nano-bio-eco-friendly hybrid energy material. Further, in the case where conventional techniques for directly growing carbon nanotubes on graphite paper and for supporting a nano-platinum catalyst on the carbon nanotubes using chemical vapor deposition (CVD) (Korean Patent Application No. 10-2007-0015801) are applied to the present invention, it is obvious that the activity of the catalyst is further increased.
The carbon nanotubes have superior electrical conductivity, specific surface area, and hydrogen storage performance, and also themselves have very high adsorption properties. As well, because carbon nanotubes have a specific surface structure, they can prevent the aggregation of metal particles when supported with the metal particles. Thus, the carbon nanotubes are expected to be used as a catalyst support. However, research into carbon nanotubes to date is mainly concerned with the synthesis thereof, and studies on the application thereof are very poor, attributable to difficulty in mass production and problems of preparation costs. Moreover, attempts to apply carbon nanotubes as a catalyst support are very few.
Accordingly, the present invention is intended to develop a high-performance supported catalyst by growing carbon nanotubes on the surface of a cellulose catalyst support and supporting various nano-metal catalysts (e.g., platinum, palladium, cobalt, molybdenum, ruthenium, etc.) on the grown carbon nanotubes, through a very simple process incurring low expenses. As such, the nano-metal catalyst is supported not through impregnation, which is typical, but through chemical vapor deposition (CVD), which is disclosed in Korean Patent Application No. 10-2007-0015801. The reason why CVD is used to support the metal catalyst particles is that the size of the catalyst particles is considerably decreased and the degree of dispersion of the catalyst particles is very high. A platinum catalyst made of precious metal is widely used for various hydrogenation and reforming reactions, and exhibits activity superior to other metal catalysts, but is problematic in terms of high preparation costs. Thus, in order to overcome these problems, it is important that the size of the platinum catalyst particles, which are a catalytic active phase, be decreased to a nano size, and that the catalyst be supported in a high dispersion state, whereby the platinum catalyst is used in a minimum amount to thus maximize the number of catalytic active sites. To this end, the surface area of the catalyst support that supports the catalyst should be very large, and further, in the supporting procedure, the catalyst metal particles should not be aggregated on the surface of the catalyst support.
To date, examples in which only cellulose fibers are used as a catalyst support through a series of treatment procedures have not yet been introduced. Similarly, U.S. Patent Application Publication No. 2006/0286434 A1 discloses that an electrically conductive carbonaceous material is incorporated into a cellulose matrix to thus prepare a cellulose composite, which is then used to form electrodes for fuel cells. Further, U.S. Pat. No. 4,253,990 discloses a method of preparing a porous catalyst support in which natural diatomite, bentonite clay, silica, cellulose fibers, corn meal, and water are mixed, extruded, pelleted, dried, and calcined.
In addition, K. Rajender Reddy et al reported the preparation of a cellulose supported palladium catalyst by incorporating commercially available microcrystalline cellulose (S. D. Fine chemicals., India) into a catalyst metal solution (Journal of molecular catalysis A: chemical 252 (2006) 12-16). Further, B. Azambre et al reported the synthesis of a carbon support through thermal treatment of commercially available microcrystalline cellulose (Aldrich) and the adjustment of the hydrophilic properties of the surface of the carbon support through a series of treatment procedures to make the carbon support suitable for use as a catalyst support (Journal of analytical and applied pyrolysis 55 (2000) 105-117).
As mentioned above, attempts to use cellulose fibers themselves as a catalyst support have not yet been made. The present invention applies cellulose, which is a resource that is abundantly present on the earth, as a catalyst support having high value, and is thus estimated to be very important in terms of nano-bio-eco-friendly techniques.